Recently, with the development of battery technology, a battery may be used as power resource in mobile communication equipment, such as portable telephone, laptop and digital camera, as well as robot, hybrid vehicle and electric vehicle, so that the battery is required to have a high capacity. However, in order to increase the battery capacity, the winding core of a battery should be thick. Generally, a plurality of relatively thin winding cores are disposed so as to ensure the saturating effect of electrolyte solution. In this case, the number of positive electrode tab (the exposed part of the positive current collector) and negative electrode tab (the exposed part of the negative current collector) increase, and the whole thickness of the electrode tab also increases, which causes it difficult to weld the electrical connection piece to the tap, thus causing sealing-off and false welding, and deteriorating the rate performance of the battery.
As shown in FIG. 1, the positive electrode tab (or negative electrode tab) 21′ of a winding core 20′ of a conventional battery is connected to the positive electrode terminal (or negative electrode terminal) of a cover plate via an electrical connection piece 22′. Because the battery may comprise a plurality of winding cores 20′, and the positive electrode tab (or negative electrode tab) 21′ of each winding core 20′ is needed to be connected to the corresponding positive electrode terminal (or negative electrode terminal) of the cover plate via an electrical connection piece 22′.
Conventionally, the electrical connection piece 22′ can be welded to only one winding core 20′. With the number of the winding cores 20′ increasing, the welding of the electrical connection piece 22′ becomes more difficult and sealing-off and false welding may be more serious.
Further, the electrical connection piece 22′ is needed to be welded to the positive tap (or negative tap) 21′ and the positive electrode terminal (or negative electrode terminal) of the cover plate via ultrasonic welding from a side surface and an ultrasonic welding seam 23′ is formed. The ultrasonic welding seam is large and occupies a large area, so that large areas at both ends of the winding core 20′ for forming positive electrode tab (the exposed part of the positive current collector) and negative electrode tab (the exposed part of the negative current collector) respectively are needed, which may reduce the volume energy density of the battery.